Multi-fingered hand devices having a structure similar to human hands comprise a plurality of finger mechanisms extending from a palm mounted on the distal end of an arm. Each of the finger mechanisms comprises a plurality of interjoint members (link members) successively connected by a plurality of finger joints.
There have heretofore been known multi-fingered hand devices of the above type which have actuators associated with the respective finger mechanisms for actuating the finger joints of the finger mechanisms. The actuators are disposed in positions (e.g., in the palm, the arm, or the like) spaced from the finger mechanisms, and are connected to the respective finger mechanisms by wires and pulleys around which the wires are trained. The wires are pulled by the respective actuators to bend the finger mechanisms. Reference should be made to Japanese laid-open patent publication No. 60-207795 and Japanese laid-open patent publication No. 6-8178, for example.
Since the conventional multi-fingered hand devices of the above type have actuators associated with the respective finger mechanisms, a large space is required for installing many actuators therein though the finger mechanisms can independently be controlled for their bending actions. Furthermore, because the wires interconnecting the finger mechanisms and the corresponding actuators are required respectively by the finger mechanisms, another space is also required for laying out the many wires therein, and the wires are laid out in a complex pattern.
One solution to the above problems would be to bias the finger mechanisms into an extended or bent position with springs or the like, join wires extending from the respective finger mechanisms to each other, and pull the joined wires with a single actuator to bend or extend the finger mechanisms.
However, when the finger mechanisms are bent to grip an object, for example, if either one of the finger mechanisms abuts against the object or another obstacle and fails to be bent further, then the other finger mechanisms are also unable to be bent, failing to grip the object properly. When the finger mechanisms are to be extended from a bent position, if one of the finger mechanisms abuts against an obstacle or the like and cannot be extended further, then the other finger mechanisms are also unable to be extended.
The present invention has been made in view of the above background. It is an object of the present invention to provide a multi-fingered hand device having a plurality of finger mechanisms that can be bent and extended through wires by a small number of actuators, which serve as drive sources for bending and extending the finger mechanisms, and can be bent and extended smoothly for gripping an object.